To those actually old enough to drive/buy their own car and have voted Sub-zero/Cool for this car...
Would you actually go out and spend £45k (c.$70k) of your own money on a 'performance' Volvo?
Probably, yeah. If I wanted a fast saloon/estate it'd be pretty high up my list. Aside from badge snobbery there's little real reason to choose anything it competes against above it (subjectively, anyway).
Saying it doesn't have the credibility of AMG or MSport is too black and white. The modern M-stuff is all well and good performance-wise but its sense of occasion has diminished somewhat these days with reams of M-kitted 318is, X5s and others on the road - and engine aside they're little different mechanically from any other BMW these days either.
I've driven a few recent AMGs too. Ballistic, and they sound pretty good. Few nice details here and there too, particularly in the cabin. But again, they feel little more intrinsically special than the regular cars they're based on. I'm really quite a fan of modern Mercs but they don't really make me feel warm inside.
You might say, "you could say that of Volvo too", except I wouldn't. The current Volvo range is jolly nice as it is, to the point I'd have a V40 over a 1-Series/A-Class/A3 and a V60 over a 5-Series/E-Class/A6 estate - and that'd continue with the Polestar. The cabins are nicer in the Volvos (and ludicrously comfortable even by the standards of the class) and I prefer the non-Premiership Footballer/drug dealery image of the Lolvo too.
There's always the "but the Merc/BMW would offer the more interactive driving feel" or something along those lines, but if I wanted that then I wouldn't be buying a big comfy saloon anyway. The Polestar is more or less exactly what I'd want from such a car.
All of which is sort of irrelevant anyway - since I voted cool on whether I find the car cool or not, and not on how good a car it is or whether it has some largely irrelevant performance deficit to the Germans. It's a fast, attractive saloon/estate that colour aside, doesn't need to shout about its abilities. And it's from Sweden, which is automatically cooler than it being from Germany.